1. Field of the Invention
This invention relates broadly to surgical instruments. More particularly, this invention relates to endoscopic surgical instruments having detachable proximal handles.
2. State of the Art
Endoscopic surgery is widely practiced throughout the world today and its acceptance is growing rapidly. In general, endoscopic surgery involves the use of a camera or magnifying lens inserted through a tube, while a cutter, dissector, or other surgical instrument is inserted through another tube for purposes of manipulating and/or cutting an internal organ or tissue under view of the surgeon. In endoscopic biopsy procedures, typically, the camera is located in one lumen of a flexible endoscope while the biopsy cutter is placed through another lumen thereof.
Most endoscopic instruments have similar configurations with a proximal handle, an actuation mechanism, and distal end effectors coupled by a flexible tube or coil through which the actuation mechanism extends. The end effectors take many forms such as grippers, cutters, forceps, dissectors and the like.
Initially, endoscopic surgical instruments were very expensive, partly because they must be very small but still durable and reliable and the materials and manufacturing methods necessary to provide these features are expensive. Recently, however, a number of "disposable" endoscopic instruments have been introduced and their use is now widely accepted. One of the advantages of disposable endoscopic instruments over reusable instruments is that because they are used only a single time, there are no sterilization problems, (i.e., no risk of cross-contamination between patients) and no concerns about the dulling or nicking of blades or wearing of parts. However, in order to justify disposing of instruments after a single use, the instruments have to be much less expensive than the reusable tools. In order to manufacture the instruments less expensively, the disposable instruments therefore use less expensive materials. As a result, the disposable instruments potentially are less durable than the reusable instruments. It is recognized, however, that the less durable components of the disposable instruments are most often parts of the distal end effectors and that the proximal handle portion of a disposable instrument is substantially as durable as the proximal handle portion of a reusable instrument. Moreover, the distal end effectors are not so fragile that they can only withstand a single use. Despite manufacturer's recommendations to the contrary, some surgeons will sterilize disposable instruments and reuse them a few times in order to reduce "per procedure costs". Ultimately, however, it is the distal portion of the instrument which wears or breaks and mandates disposal of the entire disposable instrument.
Among the disposable endoscopic instruments in use today are a number of different types of biopsy forceps devices. These devices most often include very sharp opposing jaws for grasping and tearing tissue for biopsy. The jaws are mated with one another about a clevis pin which is mounted in a clevis. The clevis extends into a housing which is crimped to the distal end of a relatively long flexible coil. The proximal end of the coil is coupled to a handle having means for articulating the jaws. The handle generally includes a central slotted shaft about which a spool is disposed. A pull wire from the jaws extends through the coil and is attached to the spool while the coil is attached to the central shaft of the handle. Movement of the spool relative to the central shaft moves the pull wire relative to the coil and thus articulates the jaws at the distal end of the coil. In use, the jaws and coil are inserted through a flexible endoscope which is already in place in the patient's body. The surgeon guides the coil and jaws to the biopsy site while a nurse holds the handle. When the surgeon has located the jaws at the appropriate place, the nurse is instructed to operate the handle to articulate the jaws and grasp a biopsy sample. At the conclusion of the biopsy procedure, the entire forceps apparatus is either disposed of or cleaned and sterilized for re-use.
The known endoscopic biopsy forceps devices of the art have the drawback that the jaws wear out long before the useful life of the handle has expired. Thus, the entire instrument must be discarded when it is only a small portion of the instrument which is inoperative.
An endoscopic biopsy forceps device with detachable proximal handle and distal portions is known and described in U.S. Pat. No. 4,763,668 to Macek et al. It is a disadvantage of the Macek et al. detachable biopsy forceps device that attachment and detachment of the proximal and distal portions requires the screwing in and out of screws and an awkward rotation of a sleeve which makes the attachment and detachment procedures cumbersome.
Co-owned U.S. Pat. No. 5,507,297 to Slater et al. discloses laparoscopic instruments having detachable proximal handle and distal portions. These instruments have a distal assembly insertable and removable from a proximal handle assembly in one step actions. The distal assembly includes a tube, end effectors coupled to the tube, and a push rod coupled to the end effectors and slidable through the tube. The proximal handle assembly includes a tube sleeve for receiving the tube, manually operable actuating means, and a latch for coupling the push rod to the actuating means. The tube sleeve is provided with a ball or blade lock for holding the tube securely in place and the tube is provided with a circumferential groove for engaging the ball or blade lock. The latch is spring loaded, hinged, and has an inclined surface for quick coupling with the push rod and an unlatching surface which when biased by an unlatching member uncouples the push rod. The push rod is provided with a mating tip which engages the latch so that the manually operable actuating means causes reciprocal movement of the push rod within the tube to operate the end effectors. Coupling and uncoupling the proximal and distal assemblies is quick, one step, and substantially automatic. However, the coupling of the tube to the lock is complicated and expensive to manufacture.
Co-owned U.S. Pat. No. 5,454,378 to Palmer et al. discloses endoscopic instruments also having one step coupling and uncoupling. The handle assembly of the instrument includes coupling devices for removably coupling the handle to a coil and to pull wires. The proximal end of the coil is provided with a mating sleeve having a circumferential groove, and the proximal ends of the pull wires are provided with a mating tip assembly. The handle assembly includes a central slotted shaft carrying a spool having a cross block which passes through the central slot of the shaft. The distal end of the shaft is provided with a spring biased latch for engaging the circumferential groove of the mating sleeve of the coil. The cross block of the spool is provided with a pair of spring biased sliders for engaging the mating tip assembly of the pull wires. The mating sleeve has a tapered proximal end so that when it is inserted into the distal end of the handle shaft, the biased latch is moved open until the sleeve is inserted to the point where the circumferential groove is engaged by the latch. The cross block is provided with an internally tapered guide and the mating tip assembly of the pull wires is tapered to be received and guided by the guide. The sliders have angled faces for receiving the mating tip and locking around it. The coil and pull wires are thus coupled to the handle in a single motion by inserting the proximal end of the coil and pull wires into the distal end of the handle shaft. The mating sleeve and mating tip assembly automatically engage-the latch and the sliders respectively and "snap" into place. During disengagement, the latch is operated by a push button at the distal end of the handle shaft. By pushing the push button, the latch releases the coil and the circumferential groove of the mating sleeve can be slid out of engagement with the latch by pulling the coil. Pulling the coil from the handle also pulls the pull wires which are coupled to the cross block containing the sliders, which in turn results in a pulling of the cross block of the spool. As the cross block moves proximally along the slotted shaft, a collar is engaged by a mechanism attached to the proximal end of the slotted shaft. The collar in turn engages angled extensions of the sliders, and forces the sliders apart, thereby releasing the mating tip assembly of the pull wires, and thus the handle from the distal assembly. While the instrument has proven effective in providing an endoscopic instrument having a handle separable from the distal assembly, the spool and shaft couplings each have a large number of parts and are expensive and complicated to manufacture. In addition, re-assembly of distal assembly into the handle requires precision alignment of the coil and pull wires relative to the spool and shaft couplings, which is time consuming.
In Europe, an endoscopic biopsy device having a detachable handle assembly is currently being marketed by Karl Schad. The device has a relatively simpler construction. The handle assembly includes a central slotted shaft carrying a spool having a cross block which passes through the central slot of the shaft and coupling devices for removably coupling the handle assembly to a coil and to a pull wire. The proximal end of the coil is provided with a substantially cylindrical connecting sleeve having internal threads and the distal end of the shaft is provided with external threads such that the connecting sleeve and the shaft are coupled together at their respective threads. The proximal end of the pull wire is provided with a mating tip assembly. The spool is provided with a spring biased latch which engages the mating tip assembly. The mating tip assembly is engaged by depressing the latch, inserting the mating tip assembly into a hole provided in the latch, and releasing the latch. While the Karl Schad device presents a viable method of constructing an endoscopic instrument having detachable handle and distal assemblies, the device is not ideal. In order to couple the handle assembly to the pull wire and to the coil, a cumbersome two step operation is required. First, the spring biased latch must be depressed in order to receive the mating tip assembly and released to engage the mating tip assembly. This is an inconvenient manner of coupling the pull wire to the spool. Next, the connecting sleeve must be inserted over the shaft and rotated many times relative to the shaft so that a secure threaded coupling is accomplished between the connecting sleeve and the shaft. This coupling method is time consuming.